movie streaming fine 20 minutes then the picture gets itchy

[Schakine]

Well i stream movies from my pc both mkv and avi to an Acer A 500 tablet
Everything fine the first twenty minutes then the pictures lags and become more static
Had increased memory on subsonic tray icon toi 1200 without success
Of course,i can watch to the end and the sound is fine but it is quite desapointing as the start is just fine
Do someone knows what i can do?
My tablet has a good memory built in and i had increase the cache to one Go without success either
Thank you